A roll pallet is a form of relatively large trolley mounted on wheels and generally has upstanding frame-like side members so that boxes or crated goods can be piled up on top of one another without falling off. Such roll pallets will, for the benefit of this specification, be referred to as "wheeled trolleys".
Wheeled trolleys are quite commonly encountered in the movement of goods between central warehouses and supermarkets and for shelf stocking. They are also in general use for handling and transporting mail bags.
The loading and unloading apparatus according to the invention is also suitable for conventional wooden pallets where the pallets have downwardly extending side portions or flanges along each edge as compared with pallets with flat under-surfaces. In fork-lift truck operations lifting and lowering is achieved by placing the fork underneath the pallet and between the downwardly extending side members. Such pallets, generally made from rough timber, may be loaded into containers by placing the downwardly extending edges or flanges of the pallet on a pair of moving belts spaced apart by the standard spacing of relatively narrow pallet flanges.
The friction between the moving track and the lower surface of the downwardly extending side walls conveys the pallet from one end of the container floor to the other. However, even in this case there is a location problem in that the side walls or flanges have to be located on the twin moving belt, in other words, the lower parts of the downwardly extending side walls have to be located directly on the moving belts and not so that the moving belts are between or outside the downwardly extending side walls.
Wheeled trolleys pose even more severe problems of guidance since it would be difficult, if not impossible, to position firstly the front wheels and then the rear wheels over the narrow moving belts which are spaced apart by the distance between each pair of wheels. Moreover, there is a maneuverability problem since wheeled trolleys of any kind may not proceed in a straight direction and may move to the left or right or traverse the container floor and are generally not easy to guide in a chosen direction.
Moving belt systems for loading and unloading boxed or crated goods are known in which the moving belt is attached to either side of the bulkhead. U.S. Pat. No. 4,111,318 to Lutz, relates to such a system which uses a number of wire cables as the moving belt, in this case a number of them extending along the vehicle or container floor or partly recessed therein. In addition, applicant's co-pending application GB 8908430.15 dated Apr. 14, 1989, relates to another form of cable conveyor more suitable for a transfer apparatus to be placed between the rear of the vehicle and the loading or unloading dock. Both the system in U.S. Pat. No. 4,111,318 and applicant's co-pending application utilize directly driven cables as the sole load carrying conveyor. Cables are not suitable for pushing loads.
In U.S. Pat. No. 4,111,318 a bulkhead is used which is moved by wire ropes attached to either side thereof and the cables are driven by winding up around drums. Thus, the bulkhead is drawn from a position at the loading end of the vehicle and movable up to the front end of the vehicle so as to protect the front wall of the container or the back section of the cab and the goods that may come into contact with the back section.
In U.S. Pat. No. 4,111,318 the bulkhead is returned for reloading by separate cables pulling it back to the loading position since cables will not function in compression and cable systems are not easy for operations where reversal of direction is required. The apparatus according to the present invention is not primarily driven by wire ropes and is therefore capable of carrying goods into and out of the container or vehicle.